Machining station, workpiece holding system, and method of machining a workpiece

ABSTRACT

The machining station can include a table; at least three robots each having a multi-axis mover secured to the table, and a gripper opposite the table, the robots being interspaced from one another on the table; and a controller. The controller controls the robots to hold a workpiece in a coordinated manner. The computer numerical command (CNC) machine-tool system machines the workpiece while the workpiece is held by the robots. The workpiece can be moved into and out from the machining station with a trolley which slidingly engages a trolley path formed within the table.

FIELD

The improvements generally relate to the field of machine-tools, andmore specifically to a workpiece holding system for holding theworkpiece during machining.

BACKGROUND

Automating machining operations is an important aspect of improvingworldwide competitiveness of some manufacturing plants, and can be vitalin industries such as the automobile or aerospace industries forinstance.

Computer numerical control (CNC) machine-tools have been developed tothis end over the last decades, and can perform multiple machiningoperations on a workpiece in a workstation. In some fields, machiningoperations must be performed within very tight dimensional tolerances.To achieve such tight dimensional tolerances, it was known to firmlysecure the workpiece on a sturdy base commonly referred to as a ‘table’,in the workstation. The machine-tools were then moved relative to theworkpiece, performing various machining tasks on the workpiece. Themovement of the machine-tools was tracked, allowing precise control in anumerical reference frame of the workstation. The overall workflow ofthe machining station also included the handling of the workpiecesbefore and after the milling operation, as well as the step of preciselydetermining the position and orientation of the workpiece in themachining station.

These known methods were very satisfactory for relatively smallcomponents. However, in some industries, there was a need to performautomated machining operations on larger components, such as aircraftwing skins or spars for instance. There thus remained room forimprovement. For instance, there remained room for improvement inhandling relatively large workpieces in the context of automatedmachining operations.

SUMMARY

There is provided a workpiece holding system for a machining station.The workpiece holding system includes three or more robots mounted on atable, and a controller adapted to control the robots in a coordinatedmanner to grab the workpiece and hold the workpiece firmly during themachining operation. The robots can have parallel kinematic movers, suchas hexapod movers for instance, which can allow the flexibility of bothmoving and orienting the grippers over three axes, providing six degreesof freedom, while simultaneously providing ruggedness and stability tohold the workpiece in a given position within very tight dimensionaltolerances while the machining operations, which impart forces andmoments on the workpiece, are performed thereon. A handling scheme isalso presented in which the workpieces are mounted to trolleys whichhave a shape mating with a shape of a corresponding cavity forming atrolley passage in the table, in a manner that a workpiece can be movedinto the machining station manually by moving the trolley, unsecuredfrom the trolley, grabbed by the coordinated action of the robots,positioned and held in a machining position, machined by themachine-tool system while it is held by the robots, freed from therobots, secured to the trolley, and manually removed from the machiningstation with the trolley in a highly productive and efficient manner.

In accordance with one aspect, there is provided a machining stationcomprising: a table; at least three robots each having a multi-axismover secured to the table, and a gripper opposite the table, the robotsbeing interspaced from one another on the table; a controller configuredand adapted to control the robots to hold a workpiece in a coordinatedmanner, based on control data; a computer numerical command (CNC)machine-tool system operable to machine the workpiece while theworkpiece is held by the plurality of robots.

In accordance with another aspect, there is provided a method ofmachining a workpiece in a machining station having a table, at leastthree robots each having a multi-axis mover secured to the table andhaving a gripper opposite the table, and a computer numerical command(CNC) machine-tool, the method comprising, positioning the workpiece inthe machining station; controlling the robots to hold the workpiece in acoordinated manner based on control data including coordinates of theworkpiece in the machining station; machining the workpiece with the CNCmachine-tool while the workpiece is held by the robots; controlling therobots to free the workpiece; removing the workpiece from the machiningstation.

In accordance with another aspect, there is provided a workpiece holdingsystem for holding a workpiece during machining with a CNC machine-tool,the workpiece holding system comprising: a table; at least three robotseach having a multi-axis mover secured to the table, and a gripperopposite the table, the robots being interspaced from one another on thetable; a controller configured and adapted to control the robots to holda workpiece in a coordinated manner, based on control data.

It will be understood that in the context of this specification, theexpression ‘controller’ is not intended to be interpreted in alimitative manner, and is explicitly intended to be construed asencompassing any suitable device for performing the automatedfunctionalities which the controller is associated to. A controller canbe embodied in the form of one or more circuits of solid-statecomponents. However, in the context of this specification, a controllerwill more likely be provided in the form of a computer having integratedcircuits. The controller can alternatively be provided in the form of aplurality of computers adapted to communicate with one another in awired or wireless manner. It will be understood that the expressions‘computer’ as used herein is not to be interpreted in a limiting manner.It is rather used in a broad sense to generally refer to the combinationof some form of one or more processing units and some form of memorysystem accessible by the processing unit(s). A computer can be apersonal computer, a smart phone, an appliance computer, etc.

It will be understood that the various functions of a controller or acomputer can be performed by hardware, by software, or by a combinationof both. For example, hardware can include logic gates included as partof a silicon chip of a processor. Software can be in the form of datasuch as computer-readable instructions stored in the memory system. Withrespect to a computer, a processing unit, a controller, or a processorchip, the expression “configured to” relates to the presence ofhardware, software, or a combination of hardware and software which isoperable to perform the associated functions.

Many further features and combinations thereof concerning the presentimprovements will appear to those skilled in the art following a readingof the instant disclosure.

DESCRIPTION OF THE FIGURES

In the figures,

FIG. 1 is an oblique view of an example of a machining station;

FIG. 2 is another oblique view thereof, with a workpiece positionedtherein;

FIGS. 3A and 3B are front elevation views thereof, showing the robotsdisengaged, and engaged, with the workpiece, respectively;

FIG. 4 is a bloc diagram of an example machining station;

FIG. 5 is a flow chart of an example machining operation;

FIGS. 6A, 6B and 6C show different workpieces held in the machiningstation;

FIG. 7 is an oblique view of a multi-axis mover;

FIG. 8A and 8B are an oblique view, and a cross-sectional view takenalong lines 8B-8B of FIG. 8A, respectively, of a gripper; and

FIG. 9 is a bloc diagram of the example machining station of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows an example of a machining station 10 having a computernumerical command (CNC) machine-tool system 12 and a workpiece holdingsystem 14. The CNC machine-tool system 12 and the workpiece holdingsystem 14 can have individual controllers and individual userinterfaces. Alternately, the controllers and/or user interfaces of themachine-tool system and of the workpiece holding system can be partiallyor more fully integrated to one another. In this example, a controller16 is provided with a user interface 18 which can be used at least forthe workpiece holding system 14.

In this embodiment, the machining station 10 also has a machiningcompartment 20 surrounded by an upper platform 22 and accessible bydoors 24. The CNC machine-tool system 12 has at least one spindle 26which can perform machining operations such as drilling, boring,chamfering or milling for instance. The spindle 26 is movable alongthree orthogonal axes forming a reference frame 28 and is orientablearound the three orthogonal axes of the reference frame 28. The spindlethus has 6 degrees of freedom.

As shown more clearly in FIGS. 2, 3A and 3B, the workpiece holdingsystem 14 has a table 30 receiving a plurality of robots 32 on a robotarea of the table 30, the robots 32 being controllable in a coordinatedmanner to grab and move/orient a workpiece 34 located in the machiningstation 10. The table 30 is integrated into a platform which also hastwo opposite lateral alleys 36 on opposite sides of the robot area. Aswill be explained below, the workpiece 34 is engaged and removed fromthe machining compartment 20 via a trolley 40 to which it can bemounted.

Indeed, a workpiece handling scheme is provided in which the workpiecesare securable to corresponding trolleys. One such trolley 40, with aworkpiece 34 mounted thereon, is shown in FIGS. 2 and 3A. The trolley 40have a wheeled base 42, an upper frame 44 to which the workpiece 34 canbe removably secured, and a vertical member 46 connecting and supportingthe upper frame 44 relative to the wheeled base 42. The table 30 has acavity forming a trolley passage 48 in the shape of an elongatedinverted-T with a trolley base channel 50 at the bottom and a trolleyslot 52 providing a vertical opening to the cavity, such as more clearlyshown in FIGS. 3A and 3B. The trolley base channel 50 has a width andheight adapted to receive the wheeled base 42 of the trolley 40, and theslot 52 is shaped to receive the vertical member 46 as the trolley 40 islengthwisely slid into the trolley passage 48. The upper frame 44 isconfigured to protrude above the table 30 and above the robots 32 whenthe trolley 40 is slid into or out from the machining compartment 20. Inthis embodiment, a portion of the table 30, and more specifically aportion of the robot area of the table 30, forms ledges 53 on both sidesof the slot 52 which protrude over corresponding portions of the basechannel 50. In this workpiece handling scheme, multiple trolleys can beused, and the additional trolleys can be used to prepare or storeworkpieces while a given workpiece is being machined. The trolleys canalso be used to temporarily store the workpieces. In the case ofrelatively flat and wide workpieces, the upper frame 44 can optionallybe pivotally mounted to the vertical member 46 to allow pivoting theworkpiece from the horizontal orientation shown to a verticalorientation and occupy less storage volume before and after themachining operation.

In an another embodiment of the invention, the trolley 40 has twovertical frames supporting and preferably connecting on the outer edgesof the upper frame 44 and relative to wheeled bases. The trolley 40 canmove on the table 30. The upper frame 44 is configured to protrude abovethe table 30 and above the robots 32 when the trolley 40 is slid into orout from the machining compartment 20, the two vertical frames passingoutside the robots 32.

As shown in FIGS. 3A and 3B, the robots 32 each have a multi-axis mover54 secured to the table 30 and a gripper 56 opposite the table. When thetrolley 40, with the workpiece 34 mounted thereon, is slid into themachining compartment 20, the robots 32 can be controlled to remain in a‘parking’ configuration such as shown in FIG. 3A, in which the grippers56 are retracted downwardly. When the workpiece 34 is in position, therobots 32 can be controlled to grab and hold the workpiece 34 by movingand operating the grippers 56. In this embodiment, the multi-axis movers54 are hexapod movers. The hexapod movers allow movement of theirrespective grippers 56 along three orthogonal axes and orientation oftheir respective grippers 56 around three orthogonal axes, effectivelyproviding six degrees of freedom to the grippers 56 within a given span.The movement span of the grippers 56 is illustrated in dashed lines inFIG. 3A. In the retracted, parking configuration shown in FIG. 3A, theupper frame 44 of the trolleys 40 clear the grippers 56 and the trolley40 can be fully inserted into the machining compartment 20, with thewheeled base 42 thereof snugly engaged with the base channel 50. Therobots 32 can hold the workpiece 34 through the upper frame 44 or/and oneach side of the upper frame 44. That depends on the size of the upperframe 44 and on the features of the workpiece 34 to hold.

In this embodiment, lateral rollers 60 are provided on the verticalmember 46 of the trolleys to snugly engage opposite lateral faces of theslot 52, providing very limited freedom of movement of the trolleys 40in the trolley passage 48 except in the longitudinal orientation.Accordingly, if the shape and dimensions of the trolley 40 is known, andthe position of the workpiece 34 on the trolley 40 is constant, with asatisfactory degree of precision, the workpiece 34 can be expected to bein a relatively precise position and orientation in the machiningcompartment 20 when the trolley 40 is slid down to the longitudinal endof the trolley passage 48. In this context, longitudinal refers to thelength of the trolley passage. The preciseness of this positioning maybe sufficient in some embodiments to activate the robots 32 to grab theworkpiece 34, and could be coded as predetermined primary location data62 (see FIG. 4) including at least partial coordinates indicative of theposition of the workpiece on the trolley. The primary location data 62can form part of control data 64 used by the controller 16 of the robots32 to automatically engage and grab corresponding locations of theworkpiece 34. The positioning could depend on the model of the workpiece34 to be machined and a user input (e.g. scanning a bar code or enteringa part number) could specify this model to the controller 16 in a mannerthat the controller 16 can find the correct primary location data 62 forthe specific workpiece model, for instance.

However, in the illustrated embodiment, a 3D scan is used to generate anat least partial 3D model of the position and orientation of theworkpiece in the machining station. This 3D model is stored in the formof primary location data 62 in a computer readable memory which isaccessible by the controller 16. Artificial vision can further beprovided as a component of a vision system 66 and recognize specificfeatures of the 3D model (e.g. reference holes, flanges, bores, edges,etc.) which can be used as references to determine the areas where thegrippers 56 are to engage the workpiece 34. Accordingly, the controller16 can control the robots 32 to engage those areas by the grippers 56,in a reference system 68 of the workpiece holding system 14. Themovement of the robots 32 are coordinated with the coordinates of theworkpiece which are included as part of the primary location data 62.The primary location data 62 can be said to form part of control data64, and the control data 64 can further include, for instance, datawhich is used to determine a path of the grippers 56 to reach theworkpiece 34, for instance.

In some embodiments, the primary location data 62, or coordinatesotherwise obtained by 3D scanning, may be used by the CNC machine-toolsystem 12 to perform the milling. However, in this embodiment where theworkpieces 34 are aeronautical components requiring a relatively highdegree of dimensional tolerances (small dimensional tolerances), thedegree of dimensional tolerances afforded by the primary location data62 was not sufficient to allow machining within the required dimensionaltolerances. Accordingly, a secondary locating system is used in thisembodiment to obtain refined coordinates of the workpiece location andorientation, in the form of refined location data 72. In thisembodiment, the secondary locating system is a probe locating system 70.The probe locating system 70 can use a first set of coordinates todetermine roughly where to execute the probing. This first set ofcoordinates can be provided in the form of the preliminary location data62, for instance.

However, in this embodiment, it was preferred, once the workpiece 34 wasgrabbed by the robots 32, to use the robots 32 to move the workpiece toa predetermined milling position made accessible to the controller 16 inthe form of workpiece positioning data 74. More specifically, thecontroller 16 can determine the difference in the position andorientation of the workpiece as indicated in the primary location data62 vs. the workpiece positioning data 74, and control the robots 32 in acoordinated manner to move the workpiece 34 to the predetermined millingposition.

The predetermined milling position can, for example, be set to be at agiven distance above the upper end of the trolleys, to avoid anyinterference between the path of the machine-tool and the trolley.Accordingly, the trolley can be left inside the machining station duringthe step of machining.

The predetermined milling position can depend on the model of theworkpiece 34, and a user interface 18 can be used to allow thecontroller 16 to select the correct workpiece positioning data 74depending on the workpiece model. The workpiece holding system 14 canthus include, as part of the user interface 18, means to enter a partnumber or to scan a barcode or RFID tag, for instance, which can bereferred to as an identification subsystem 76 for workpieceidentification. In this embodiment, the workpiece positioning data 74 ismade available to the probe locating system 70 and used by the probelocating system 70 as the first set of rough coordinates based uponwhich the probing routine is executed.

The probed locating system 70 provides a refined indication of theposition and orientation of the workpiece in the reference system 28 ofthe probe locating system 70, which can be stored in the form of refinedposition data 72. It can even provide information of the shape of theworkpiece, as, particularly in the context of large or otherwisesomewhat flexible workpieces, the exact shape of the workpiece 34 mayhave flexed or warped relative to the theoretical shape for theworkpiece model. The refined position data 72 can be made available tothe CNC machine-tool system 12 to perform the machining operation on theworkpiece 34 being held by the robots 32 within satisfactorily tighttolerances. Typically, the CNC machine-tool system 12 and the probelocating system 70 are precisely adjusted to be in virtually the samereference system 28. The probe locating system 70 can require theposition and orientation of the part to be known within a certaintolerance (e.g. ±0.125″), prior to commencing the probing routine, whichwas achieved with the combination of the vision system and degree ofprecision afforded by robot movement (including vacuum gripper systemwhich will be detailed below) in this specific embodiment.

FIG. 5 is a flowchart illustrating the different steps for performingthe machining operation. The workpiece is positioned 78 in the machiningstation 10, which can be performed via the trolley 40 manipulated by anoperator. Indeed, as seen in FIG. 2, the trolley 40 can be engaged intothe trolley passage 48 within the table 30. The vision system 66 can beactivated to obtain primary location data 62, and the robots 32 can beactivated 82 to grab the workpiece 34 based on this primary locationdata 62. The operator can then enter the machining station and walkalong the alleys 36 on either side of the robot area, and unclamp theworkpiece 34 from the trolley 40. The robots 32 can then be operated tomove 84 the workpiece 34 to the milling position. The probe locatingsystem 70 can be used to obtain 86 a refined coordinate set of theposition, shape and orientation of the workpiece 34 in the referencesystem of the CNC machine-tool system 12, and the CNC machine-toolsystem 12 can be operated 88 to machine the workpiece 34 based on therefined set of coordinates, while the workpiece 34 is firmly held in themachining position by the robots 32. Machining data 94 can be used bythe CNC machine-tool system 12 to determine a sequence of steps, andtool paths, to perform the machining sequence/operation. The robots 32are then controlled to release 90 the workpiece 34, which can beperformed after an operator has reclamped the workpiece 34 to thetrolley 40 for instance (after the robots have moved the workpiece 34back to the trolley position in the scenario where the workpiece wasmoved to the milling position at step 84). The workpiece 34, and itssupporting trolley 40, can then be removed from the machining station92. It will be noted that in the embodiment illustrated, the refinedlocation data can either be used to adjust the orientation/position ofthe coordinates in the reference frame of the machine-tool, or can beused by the controller to move the workpiece again, and more preciselyconform to the theoretical machining position, for instance, withoutaffecting the reference frame of the machine-tool.

Reference can be made to the bloc diagram shown in FIG. 4 to assist inthe comprehension of the interactions between the various components,often computerized instances, at work in this embodiment. For instance,in some embodiments, it can be required, when the spindle of the CNCmachine-tool system 12 reaches a given area of the workpiece 34, to freea specific one of the robots engaged with that given area from theworkpiece 34, and move the robot out from interference with the toolpath, for instance. The robot can be disengaged from a given area on theworkpiece, moved away from that area, and then be re-engaged with thatarea once the interfering machining operation has ended. In an alternateembodiment, the robot can be disengaged from a first area, moved to asecond area, and be engaged with the second area while a potentiallyinterfering machining operation is conducted in the vicinity of thefirst area.

In a scenario where the machine tool controller 96 and the workpieceholding system controller 16 are embodied as separate controllers, thisrequires communication between these controllers. To this end, themachining data 94 can be made available to the workpiece holding systemcontroller 16, which can determine when a given robot must be disengagedand cleared from a tool path, when the robot can be safely re-engagedwith the workpiece, and control the given robot accordingly, forinstance. Alternately, the machine-tool controller and the workpieceholding system controller can be integrated as part of a singlecontroller.

FIG. 6A, 6B and 6C are views illustrating the flexibility of theworkpiece holding system. Indeed, in this specific embodiment, theworkpiece holding system has 24 robots, 12 on each respective side, allinterspaced from one another on the table, and the mobility of thegrippers afforded by the movers allows to grab various components.Indeed, in FIG. 6A, the robots are operated to grab a left wing skin,whereas in FIG. 6B, the same set of robots is used to grab a right wingskin. In FIG. 6C, the same set of robots is used to grab a spar.

Indeed, in most embodiments considered, there will be significantly morethan three robots which require movement in a coordinated manner.Particular challenges can arise in controlling the cooperating action ofnumerous robots. Indeed, it was found that sub-controller units (e.g.processors) could be used to control the cooperating action of robots ofa given robot group such as shown in FIG. 4. However, robot groups weretypically limited to four robots such as shown in FIG. 9, managing thecooperating action of multiple sub-controller units and thus multiplerobot groups can be performed by application software provided by therobot manufacturer. Indeed, various embodiments of the workpiece holdingsystem will include more than 5 robots, preferably more than 10 robots,more preferably more than 15 robots, and can require coordinationbetween 2 sub-controller units, between 3 sub-controller units, orbetween more than 3 sub-controller units.

In this specific embodiment, 4 to 6 of the robots are equipped with 3Dscanners as part of the vision system. These robots can grab theworkpiece and move the workpiece close to the predetermined machiningposition. The remaining robots can then join the support effort, afterwhich the probing routine can be used to do the final coordinate systemadjustments. It will be understood that in alternate embodiments, thevision system can be based on one or more 2D cameras instead of 3Dscanner. For instance, Fanuc TM provides a 2D vision system which can befound suitable in some embodiments, one of which will be presented infurther detail below in relation with FIG. 9.

FIG. 7 shows an example of a multi-axis mover 54. In this example, themulti-axis mover is a hexapod and includes 6 extensible members eachhaving a first end pivotally connected to the base and a second endpivotally connected to the gripper portion, in a configuration allowingboth tilting and displacement of the gripper along three orthogonalaxes, providing the gripper with six degrees of freedom. Indeed, eachone of the 6 extensible members is independently operable by thecontroller 16. In this specific embodiment, the multi-axis movers areparallel kinematic robots of the hexapod type which can be obtained froma specialized manufacturer such as Fanuc for instance, and were found toprovide satisfactory operability. Indeed, the parallel kinematic of theparallel kinematic robots of the hexapod type can provide satisfactoryrigidity and repeatability, while allowing orienting the end effectorwith some degree of rotation around all three axes. Other suitablemovers can be used in alternate embodiments

FIG. 8A shows an example of a gripper 56 which can be used as an endeffectors of the robots 32 illustrated in FIGS. 3A and 3B. In thisembodiment, the gripper is of the astrictive type and includes a vacuumcup securable to a flat portion of the workpiece. More specifically, thelip of the vacuum cup can form a sealed compartment against theworkpiece when engaged therewith, and a vacuum system which can have oneor more vacuum generators 96 is used to reduce the air pressure withinthe sealed compartment and thus generate a vacuum force holding theworkpiece against the gripper. Depending on the embodiment, the numberof robots per vacuum generator can vary. In this embodiment, it wasfound satisfactory to provide one or more vacuum generators which eachservice a plurality of grippers, but each gripper was provided with avalve allowing to control the strength of the vacuum individually, on aper robot basis, forming part of an intelligent vacuum system.

In this specific embodiment, the vacuum cup is made of a flexible,resilient material, and the relative distance between the robot and theworkpiece held by the robot can vary based on this flexibility andoperating conditions. Such variations in the relative distance between agiven robot and the workpiece it holds was a source of positioninguncertainty in the reference frame of the robots. Accordingly, a linearsensor 98 was provided with each one of the grippers to obtain a precisemeasurement of the exact distance between the face of the part and therobot, in the orientation of the axis of the linear sensor. As shown inFIG. 4, the reading of the linear sensors 98 was provided to thecontroller in the form of control data. Accordingly, using this data,the controller may be operated to move the workpiece more precisely tothe predetermined milling position, for instance, or relativecoordinates between the robots and the actual position of the workpiececan be otherwise corrected or compensated. More specifically, in thisembodiment, the step of positioning the workpiece in the machiningposition can include determining any change in the linear sensorreadings between the initial position and the milling position, andmoving the grippers to correct any such change. Alternately, gripperscan be moved to correct any change in the linear sensor readings whichcould occur due to stresses imparted to the workpiece during themachining operation, in real time, for instance. This gripper type wasfound to provide satisfactory gripping capability in the embodimentshown in FIG. 1, but it will be understood that other gripper types canbe used in other embodiments. Moreover, more than one gripper, possiblyof different gripper types, can be used as the end effector per robot ifdesired. For instance, a clamp gripper can be used in addition to avacuum cup for a given robot, or for all robots, for instance. Thegripper type or types can vary from one robot to another within a givenworkpiece holding system embodiment.

Indeed, the exact type of gripper can be selected from the followinggeneral categories: impactive—e.g. jaws, clamps or claws whichphysically grasp by direct impact upon the object; ingressive—pins,needles or hackles which physically penetrate the surface of the object(e.g. an aperture or bore of the workpiece); astrictive—forces appliedto the objects surface (e.g. by vacuum, magneto- or electroadhesion);and contigutive—requiring direct contact for adhesion to take place(e.g. surface tension or freezing).

Additional detail will now be provided with respect to a specificimplementation, with reference to FIG. 9. The workpiece holding systemcontroller 16 can be provided together with HMI software. Thefunctionality can be implemented using the robot controller integratedfeature from the robot manufacturer that includes vision, guidancesoftware, vision calibration grids, camera software. In this embodiment,the vision system performs a 2D scan. For instance Fanuc can provide akit that includes : iRVision GigE 2D Guidance including iRVision-0010 G,iRVision 2D Guidance Software RTL-R685, vision label set VO-1800-560,vision calibration grids VO-1800-023, R-30iB iRVision eDoc CDMCROBIRVN06121E, iRVision GigE Camera Software Option RTL-R697, GigEStandard Resolution Camera Bundle GIGESTD_CAM_BDL, and Edmund Optics12MM High Res Lens #NT58-001Hi-Res LENSO000000030O. An oval shapedvacuum cup can be used to achieve a satisfactory holding force. The ovalshape can provide large surface but can still be set in relativelynarrow areas. Combined with the ability of the robot to orient the cupnormal to the part surface and with its length in a given orientation,such oval vacuum cups can results into an agile tooling. The vacuum cupscan be mounted on the robot flange using an extension to reach theworkpiece while on the trolleys and to be able to lift it from thetrolley without collision of the robot head with the trolleys frame. Thevacuum cup can be equipped with a Z-axis distance sensor in the form ofa linear scale based touch sensor such as made available from aspecialized sensor manufacturer. This has been used with good results.Based on the reading of each sensor, the robots can be repositioned tobring the workpiece closer to the predetermined (theoretical) millingposition, for instance. The operation can be performed in the followingsequence: i) Secure a just drilled workpiece on the trolley; ii) pullthe trolley out of the machine; iii) undo clamping (can be done whileprevious workpiece is being machined); iv) Push trolley into position onthe machine; v) Vision system gets targets and 4 robots pick-up thepart; vi) Workpiece is moved to theoretical/predetermined millingposition +/−0.125″; vii) The rest of the robots move totheoretical/predetermined milling position and grab the part; viii)Z-Axis position is adjusted based on sensor reading; ix) Part findingprobing routine adjusts the program frame. A tooling interface showingthe fixture in a simulation mode can be used to enable the operator toclearly see the fixture status and what will be the next move in theset-up program. A manual mode can also be provided in which each robotcan be individually selected, and manual moves can be previsualized insimulation mode and then applied. The motions can be controlled in themachine X-Y-Z coordinate system. The main controller can include aprogram runnable by a last generation PC. A Set-up program can be usedto define the robotic tooling configuration. Commands can be imbedded inthe workpiece-cutting program and can activate the different functionsof the robots. There can also be commands to validate the set-up vs. theworkpiece program, and the workpiece origin. Forced commands can also beprovided. Manual mode can be used to send commands entered manually tothe actuator. The manual mode can be used by the operator and themaintenance personnel. Such commands can be executed either from themain HMI or using a Teach-pendant available from the robot manufacturer,and can includes moving the end effector in X-Y-Z, or tilting aroundX-Y-Z. Automatic commands can be used to send commands to the robotsfrom the set-up program. The set-up program and the drilling program canbe selected automatically based on a bar-code reading of the work-orderor from a production management screen for instance, to ensurecoordination of the drilling and fixture program. The set-up program maybe sequenced so that the part can be lifted first, then positioned, andthen conformed to theoretical milling position in steps. Commands forpositioning, sensor reading and vacuum control can be provided. CNCcommand mode can be used to send such commands from the drilling programin case that during the drilling process a vacuum cup need to beretracted or repositioned. To facilitate set-up and maintenance, aHand-Held Teach pendant can be supplied. This pendant can be connectedto any of the six robot controller to move manually any of the 24robots. An individual compact vacuum generator unit can be installed oneach actuator close to the suction pads. The vacuum cups can havedimensions of 55 mm×150 mm (2″×5.9″) and a holding force of 125 lbf@27in Hg, for example. The units can use compressed air to generate vacuumair supply, and have the following features for instance : vacuumlevel=0.9 bar; pressurized air; integrated analog vacuum sensor; vacuumlevel adjustable at each actuator from operator station; low airconsumption—for 24 actuators; continuous=0.8 m3/hr@5 bar; intermittent—2to 3 minutes=2.64 m3/hr@5 bar; check valves and intelligent control tomaintain vacuum. A through-type silencer can be favored to reducelikelihood of clogging. Analog vacuum monitoring can be provided. Theflexible adjustable vacuum system can allows the end user to set theproper level of vacuum to a specific actuator or specific zone. Theproposed vacuum system can be adjustable and easily settable with asoftware interface. Vacuum analog sensors can be used monitor the vacuumlevel applied to the part. In the software, each vacuum level value willbe visible as soon as the mouse cursor is pointed over the relevantactuator in the monitoring display. The software can provide for vacuumalarm signal to be easily visible by a specific color and also by thedisplay of a message on the main operator screen. Anything in betweencan be illustrated as a warning zone shown by the color yellow on themonitoring display. A programming and simulation package can beprovided, which can include the following features, for instance: ICAMsoftware to create a CATIA Template; CATprocess to include the indexelements and options to position the workpiece on machine using 2indexes; CATIA NC programmer can use this template to indicate theworkpiece indexing and support frame of the workpiece and then createpoints where he desires to have the hexapod to touch the workpiece; ICAMExtractor can take the information and sends it to ICAM Virtual Machineenvironment; ICAM Virtual Machine can show the part in position onmachine; ICAM Virtual Machine can calculate the position of thedifferent Hexapod heads and display only the Hexapod head (not the armarticulation below—not needed in the case of hexapods in thisconfiguration because no possible collisions); in case of collision ICAMVirtual Machine can show the collision of the vacuum heads; ICAM offersthe possibility to the user to indicate a new position of the Hexapodhead entering a DeltaX and DeltaY value (ICAM to recalculate appropriateHead position relatively to surface normal; ICAM Post/Simulation cangenerates two files including i) one with point and vector position ofeach Hexapod to be positioned at and ii) one with the G code drillingprogram; and a special VM application with dialog boxes, user interfaceand documentation. ICAM can create: i) The related PP/VM/MRS (Postmachine model integration, indexes and template tests, & Simulation aswell as dialog boxes, user interface, documentation); ii) Delivers theCATIA related CATProcess template; iii) Post-processor and UHF relateddocumentation. The ICAM solution can: i) Allow the user to repositionthe Hexapod support without going back to CATIA CatProcess to do it; ii)provided a history file generated from user decision from ICAM VirtualMachine session are kept to ensure we can repost the same job in samecondition—providing exact same output. The controller can include onemain HMI PC and 6 robot sub-controller units. In alternate embodiments,another vision system can be used. For instance, a vision systemprovided by Cognex or by Sick can be used, or a generic camera systemwith an open architecture can be used, for instance. It can beadvantageous to integrate the vision system to the controller in thecontext of functions such as re-calculation of gripperpaths/coordinates, for instance.

As can be understood, the examples described above and illustrated areintended to be exemplary only. The scope is indicated by the appendedclaims.

What is claimed is:
 1. A machining station comprising: a table; at leastthree robots each having a multi-axis mover secured to the table, and agripper opposite the table, the robots being interspaced from oneanother on the table; a controller configured and adapted toindependently control each one of the robots to hold a workpiece in acoordinated manner, based on control data; a computer numerical command(CNC) machine-tool system operable to machine the workpiece while theworkpiece is held by the plurality of robots.
 2. The machining stationof claim 1 wherein the table has an elongated cavity forming a trolleypath, the trolley path being adapted to receive a portion of the trolleyin longitudinal sliding engagement with the table, wherein the workpiececan be secured to the trolley to move the workpiece into and out fromthe machining table with the trolley.
 3. The machining station of claim2 wherein the elongated cavity has an inverted T shape cross-section,with a lower channel adapted to receive a wheeled base of the trolley,and a central slot adapted to receive a vertical member of the trolley,the vertical member of the trolley leading to an upper frame adapted toreceive the workpiece secured thereon.
 4. The machining station of claim3 wherein the vertical member of said trolley has rollers on oppositesides, said rollers being matingly configured in a manner to engagecorresponding opposite faces of said slot.
 5. The machining station ofclaim 3 provided in combination with a plurality of said trolleys. 6.The machining station of claim 3 comprising at least four robots on eachside of said slot, further comprising an alley on each side of the slotalongside the corresponding robots, opposite the slot.
 7. The machiningstation of claim 1 comprising at least 10 of said robots, wherein thecontroller includes at least two sub-controllers, each of saidsub-controllers controlling the operation of a sub-group of said robots.8. The machining station of claim 1 wherein said controller isconfigured and adapted to control said robots based on control data,said control data including primary location data indicative of theposition and orientation of the workpiece in the machining station. 9.The machining station of claim 8 further comprising a vision systemadapted to perform a scan including at least partial coordinates of theworkpiece in the machining station, configured and adapted to providesaid at least partial coordinates in the form of said primary locationdata.
 10. The machining station of claim 8 wherein said control datafurther comprises predetermined milling coordinates indicative of apredetermined milling position and orientation for said workpiece, saidcontroller being configured and adapted to move said workpiece from saidprimary position and orientation to said predetermined milling positionand orientation based on said primary location data and on saidpredetermined milling coordinates; wherein said predetermined millingposition and orientation is above a height of the trolley to avoidinterference between the CNC machine tool and the trolley.
 11. Themachining station of claim 8 further comprising a probe locating systemadapted to provide refined location data indicative of the location ofthe workpiece, and being operable based on the primary location data,the CNC machine tool system being operable to machine the workpiecebased on the refined location data.
 12. The machining station of claim 1wherein the multi-axis mover is a parallel kinematic mover and includes6 extensible members operable by the controller, each having a first endpivotally connected to the table and a second end pivotally connected tothe gripper portion, in a configuration allowing both tilting anddisplacement of the gripper along three orthogonal axes.
 13. Themachining station of claim 1 wherein the gripper includes a vacuum cupsecurable to a flat portion of the workpiece by suction thereagainst.14. The machining station of claim 13 wherein the gripper furtherincludes a length gauge having a measurement axis oriented normal to aplane of the vacuum cup.
 15. The machining station of claim 14 whereinsaid controller is configured and adapted to adjust the position of thegrippers based on a measurement received from the length gauges.
 16. Themachining station of claim 1 wherein the controller is further operableto control the selective disengagement and re-engagement of anindividual one of said robots upon determination that a tool path ofsaid CNC machine system interferes with the position of that robot whenit is engaged, said disengagement and re-engagement being coordinatedwith the execution of the tool path.
 17. The machining station of claim16 wherein said disengagement and re-engagement includes removing anindividual one of said robots from a first area on the workpiece andthen engaging it with another area of the workpiece.
 18. The machiningstation of claim 1 further comprising an identification subsystemconfigured and adapted to receive an input, and obtain data concerningthe workpiece based on said input.
 19. The machining station of claim 18wherein said data concerning the workpiece includes predeterminedmilling coordinates of said workpiece.
 20. A method of machining aworkpiece in a machining station having a table, at least three robotseach having a multi-axis mover secured to the table and having a gripperopposite the table, and a computer numerical command (CNC) machine-tool,the method comprising, positioning the workpiece in the machiningstation; controlling the robots to hold the workpiece in a coordinatedmanner, including controlling the robots independently from one anotheralong different paths, based on control data, said control dataincluding coordinates of the workpiece in the machining station;machining the workpiece with the CNC machine-tool while the workpiece isheld by the robots; controlling the robots to free the workpiece;removing the workpiece from the machining station. 21-34. (canceled)